Vertical disconjugacy during reading in dyslexic and non-dyslexic children.

Purpose The objective of this study was to explore vertical binocular coordination in dyslexic and non-dyslexic children during saccades and post-saccadic fixation period while reading a text. Methods Binocular eye movements were recorded by an infrared system (Mobile T2 ® , SuriCog) in thirty-six dyslexic children from 7.3 to 13.6 years of age (mean age: 10.4 ± 0.3 years) who were asked to silently read a four-line text during binocular viewing. Data were compared to those of thirty-six age-matched non-dyslexic children. Results Vertical disconjugacy during post-saccadic fixation was higher in dyslexic children with respect to non-dyslexic children group. Vertical disconjugacy was not age-dependent either for dyslexic children or for non-dyslexic children. Conclusions The poor binocular vertical coordination observed in dyslexic children while reading could suggest a deficiency in the cerebellum and/or extra-ocular muscles involved in vertical eye alignment. Moreover, the fact that this vertical binocular coordination was not age-dependent could be due to an abnormal eye position and/or to a dysfunction of midbrain structures involved in vertical vergences. [ABSTRACT FROM AUTHOR]